Improving HTTP security at the Flying Circus

We now know that the secret services employ extended eavesdropping techniques to scan and analyze nearly all Internet traffic. This worries us since we want to keep our customers’ data confidential. We get a lot of questions about how secure sites hosted at the Flying Circus are. As security has many aspects, I would like to focus on one question in this post: How secure is our HTTPS encryption? In other words, is it likely that some third party sitting in the transmission path is able to decrypt traffic between our server and the user’s browser?

We have checked everything twice to ensure a good level of security with the default configuration of our web server role. Of course no-one can guarantee absolute security, but this is what we do currently:

We have improved the web server configuration so that HTTPS web sites still maintain an ‘A’ rating at SSL Labs. They have recently tightened their check criteria in the light of Snowden’s revelations on NSA practices. An ‘A’ rating means that the encryption is still very hard to break.

We use only open-source software. There are reports that secret services try to get back doors into security products to intercept traffic after it has been decrypted. Commercial security devices are a black box: You must trust them not to forward your data elsewhere. In contrast, open source software uses only published source code. The sources are read and used by a world-wide community of developers, who are in general very security aware. We compile the source code by ourselves. Although it might be possible to hide an cuckoo’s egg in the source code so advanced that it does even not get recognized by experts, this is highly unlikely.

We are in the process of switching on HTTP Strict Transport Security (HSTS) for all HTTPS-only sites. This means that web browsers are told to reject unencrypted connections to such a site.

We employ perfect forward secrecy (PFS). This means that even when captured (encrypted) traffic is stored and there will be a decryption attack available in the future, past traffic will still be undecipherable. Note that not all browsers support PFS; for example, some old IE versions on Windows XP feature only insufficient crypto. We think that it is better to reject encrypted connections from broken systems than lulling users into a false sense of security.

What is not so good currently:

We are not able to support the newest encryption suite Transport Layer Security 1.2 (TLS 1.2). To get this running, we must upgrade some shared libraries which are central to our OS deployment. This will probably take place during our next major OS upgrade at the end of the year. TLS 1.2 is more resistant against some advanced attacks but is not supported by all browsers.

To summarize: we have implemented decent security measures to prevent third parties to decipher encrypted web traffic. Our ‘A’ rating with SSL Labs is better than the majority of web sites today. There is still a library upgrade pending, but we have it already on our list.